Making steel washers
= Introduction = According to ancient manuscripts ballista washers were cast from bronze. However, some washers found from archaeological excavations were forged from steel. = Forging washers (method 1) = Forging the washer core First make a template around which you'll forge the washer core. Next take a long, flat piece of steel that has the appropriate thickness and height for the washer core and heat it in the forge: Forge the piece round over the horn of the anvil. At this point it probably looks something like this: Reheat the piece and forge it around the template: At this point you can cut the excess away: Finally reheat the piece again and forge it tightly against the template to make sure it's as round as possible. Then remove it from the template: Welding the washer core seam Closing the seam in the washer core is trivial using modern welding techniques. Forge welding is a cleaner alternative for more competent blacksmiths, although there's always the risk of deforming the washer while doing it. Start by attaching the washer core to a bench vise: Weld the seam: Grind of the excess material: Now the washer core is ready. Forging the washer rim First make a template around which you forge the washer rim. Here we use the old type, but the new type is easier to use and more precise. Start by forging the rim partially round on top of the anvil horn, flattening it periodically: After second heating the rim should be almost round: After heating the rim third time you should it should be able to beat it round over the template: Now just cut of excess material. Then heat once more, flatten the rim and make sure it follows the contours of the template perfectly. The results should look like this: Polishing washer rims The washer rim has to be very smooth to rotate properly under high pressure from the springs. The first step to ensuring proper operation of the washer rim is to forge it perfectly flat. The second step is to smoothen the rim with a coarse grinding stone: Grind the underside of the rim, periodically rotating the rim. This ensures all high points are leveled down. The results should look like this: If necessary, continue polishing with progressively finer grades of sand paper attached to a flat wooden block. Attaching washer rim to the core Once washer's rim and core are ready, make sure that they fit together tightly: Once that's taken care of it's time to weld the components together. It's important to place the rim so that it's * At exactly correct height * Perpendicular to the washer core (=in 90 degree angle) This is easy to accomplish by placing the core on a flat (steel) surface and placing two small, identical rectangular pieces of steel on both sides of the washer. These pieces make sure the rim is not leaning anywhere, and that it's at the correct height. Once this is taken care of, weld the core and rim together. NOTE: Only weld from the top or you'll have a hard time grinding away excess steel from beneath the rim later. Making the slots for washer bars Making the slots for washer bars is the next step. A good way to speed up the process is to use a slot cutting template. If you don't have one, use a hacksaw to make two cuts across the washer core at the top. The cuts should be parallel to the imaginary line that goes through the center of the circle: Once the cuts are finished, drill away the "root" of the part remaining between cuts: Next use a cold chisel and a hammer to remove this excess part: Alternatively you could use an angle grinder now that the accurate work is done. Now all that's left is to finish off the work with a file. The end result should look like this: NOTE: Make sure that the finished slot is exactly vertical: if the washer bar is leaning left or right a considerable amount, it may not withstand the pressure of the springs. Also, it will reduce the amount of space there is for the spring cord. Fitting the washer to the field-frame ring The final step in making the washers is fitting them with the field-frame rings. The amount of fitting depends on how symmetric the washer cores and field-frame rings are. In case both are forged, there's considerable amount of fitting to be done. Most of this work can be done with good flat file combined with a round one. Just make sure you don't remove too much material so that the washer feels loose, although the tension of the springs should center the washer just fine. Category:backup Category:cheiroballistra Category:Practical Category:Steel Category:Metalworking Category:Washer